Watt-hour meter with uniform damping adjustments



March 7, 1939. s s GREEN 2,149,885

WATT-HOUR METER WITH UNIFORM DAMPING ADJUSTMENTS Filed Feb. 16, 1938 MMHHMMEEMMMMB E 26 ava/2607".- 5 az/zl gg 5. G/"ee/z Patented Mar. 7, 1939.

WATT-HOUR METER WITH UNIFORM DAMP- ING ADJUSTMENTS Stanley S. Green, La Fayette, Ind., assignor to Duncan Electric Manufacturing Company,

La Fayette, Ind., a corporation of Illinois Application February 16, 1938, Serial No. 190,726

8 Claims.

This invention relates to watt-hour meters and particularly to the mounting and adjustment of the damping magnets of such meters.

Applicant has previously worked out several 5 very satisfactory forms of damping adjustment as disclosed in his copending applications Serial Nos. 37,669, 129,585, 183,433, the first of which was filed August 24, 1935, and all of which are copending with the present application so that it relates back to their filing dates for any common subject matter. The first form was applied to old style damping magnets in which the damping flux is obtained from a pair of magnets with each magnet straddling the disc and the two magnets positioned so that their four poles are close to one another. Subsequent forms and the present invention are concerned primarily with providing equally satisfactory adjustment for a different type of damping magnet in which a. single magnet is used, positioned entirely above the disc with a magnetic armature positioned below the disc. This magnetic armature is a soft iron bar which forms a low reluctance path for the magnetic flux of'the magnet so that this magnetic flux, instead of passing mainly from one pole of the magnet directly to the other, passes mainly from one pole of the magnet down through the disc to the armature, through the armature and back up through the disc from the armature to the other pole of the magnet.

The present application discloses a modified form of this invention which is especially suitable for certain types of meters and is simpler in some respects than some of those shown in my recent applications, and is believed to give still greater ease of adjustments than the others.

The present damping assembly is designed primarily for a single phase meter in which plenty of space is available and in which one relatively powerful electromagnetic driving unit drives the disc and a single magnet retards the disc. With this arrangement it is desirable to get the utmost damping torque possible from the single damping magnet. Accordingly, the present invention utilizes the principle of adjusting the armature as disclosed in my copending application Serial No. 129,585, filed March 8, 1937. In using the adjustable armature principle it is somewhat diflicult to obtain a simple dependable construction in which the range of adjustment is adequate and adjustment is sufiiciently gradual to facilitate very fine adjustments and in which there is no backlash or other cause of variation. An object of the present invention is therefore to provide an armature construction meeting these til needs and a mounting for the armature which will be sufficiently sturdy to prevent the introduction of variations due to the mounting of the armature.

Another object of the present invention is to provide an adjustable armature in which the rate of change is relatively uniform through all, or at least most, of the range of adjustment. This is very advantageous since the meter adjuster soon learns how much to turn the adjusting screw for a given percentage of error, and can therefore make the adjustments more rapidly.

Additional objects and advantages will be apparent from the following description and from the drawing, in which: I

Fig. 1 is a side elevation of the meter mechanism embodying this invention.

Fig. 2 is a fragmentary front elevationof the structure shown in Fig. 1, some parts being reby table l6.

The driving unit ll may be of a conventional type including a laminated core structure which may be secured to the meter base, not

shown.

The disc 12, the magnet l3 and the armature H-IS-IG are all carried by the frame [9 which is secured to the laminations ll.

this connection it may be observed that the frame includes a portion above the disc and a portion below the disc connected together by portions 2| extending around the edges of the disc and one of which extends between the poles of the magnet l3. The portion above the disc includes an enlarged fiat surface 22 against which the magnet l3 rests, being secured by screw 23. A plate or washer 24 is positioned between the head of the screw and the magnet I 3 and serves also to clamp a temperature compensating plate (not shown) across the legs of the magnet. The lower portion of the frame l9 includes a bed 26 on which the armature assembly is mounted.

The armature assembly includes the blocks I4 and I5 and table l6 as well as the adjustment control means.

l6 whilethe-block I4 is fixed in position thereon movement of the block I5 would have a very by screws 28. These screws pass through the table I 3 and screw into the block 14 so that the table I3 is clamped between the block II and the bed 28 The blocks I4 and It and table It are all preferably formed of an iron or steel of high permeability and low retentivity.

To slide the block I! along the table IS a screw 3| is threaded through it and journaled at the rear end of block ll as seen at 32. The remainder of the bore of block M is oversize with respect to the screw 3| so as to permit flexing of the screw 3|. The screw 3| is flexed by being held down at one end by block I4 and atv the other end by a journal bracket 34 which hooks under the table It and is secured thereto by a screw 35. This flexing of the screw 3| causes it to engage the block IS with resilient pressure thereby eliminating any play or backlash between the threads of the screw 3| and the threads of the block l5.

It is also highly desirable to eliminate backlash in the form of endwise play in the screw H. To this end the screw is provided with an annular slot 31 into which a bushing 38 is swedged with such pressure as to cause the metal to fiow into the slot so that it will remain in firm contact with both the screw 3! and the Journal bracket 34.

It will be apparent .that a convenient order of assembly of the damping armature is to insert the screw 3i through the journal bracket 34, apply bushing 38 and press it into the slot 31, screw the movable block I5 onto the screw 3|, and then apply all of this assembly to the table l6, securing it in place with the screw 35. The block it may then be slipped over the free end of the screw 3| and the assembly is ready for application to the bed 26 by passing the screws 29 therethrough and through table l6 and into the block I4. The screws 29 will draw the block l4 down tightly against the table "5 against the resiliency of the screw 3|.

It will be observed that in this manner backlash is completely eliminated from the armature assembly. The resilient distortion of the screw 3| maintains a resilient pressure between the threads of the block l5 and the screw 3|, thus eliminating play at this point, and the tight bushing 38 maintains a corresponding pressure between the screw 3| and the journal bracket 34, eliminating play at this point. This makes it possible to make an adjustment of the armature block I5 in one direction and to know that even a very slight turn of the screw 3i in the opposite direction will have the expected adjusting effect. In making extremely fine adjustments this is a very important feature from the standpoint of convenience.

When armature blocks such as the blocks l4 and I5 are separated, the adjusting efiect is ordinarily extremely great. This can be understood by remembering that the useful path for the magnetic flux is from one pole of the magnet l3, down through the disc l2, along the great adjusting effect. This would make extremely delicate adjustment quite difflcult. In my prior applications I have disclosed various ways for overcoming this diillculty but the mantable I 8 is made 01' a magnetic material, 1. e., a

material similar to that 01' which the blocks I4 and I! are formed. The result is that when the block I! is separated from the block l4, there is no complete air gap formed but a path of fairly low reluctance is maintained from block it through table IE to block H. The reluctance of the path through the table I6 is so low that the decrease of flux as the blocks l4 and I5 are separated is quite gradual, thus facilitating very fine adjustments.

As a matter of fact, it appears that the decrease in fiux is so gradual that a substantial portion of the adjustment comes from deconcentrating the magnetic fields. In order that this may be understood it should be explained that the maximum damping torque is obtained only when the opposed magnetic fields cutting the'disc (i. e., the flux going up through the disc and the fiux going down through the disc) are concentrated as closely together as possible so that a given portion of the disc will pass very rapidly from the flux in one direction to the fiux in the other direction. This sudden change in the direction of flux passing through a given portion of the rotating disc produces the eddy currents within the disc which are necessary to the retarding action. With a given amount of flux passing through the disc the value of the damping torque produced by this flux depends on the suddenness with which a given portion of the disc passes from one field of flux to the opposite field of flux. When the block I5 is slid outwardly or to the right as seen in Fig. 4, it causes the field of flux passing between it and the pole of the magnet l3 above it to move outwardly also, thus separating a substantial portion of this field from the field passing between the other pole of the magnet and the block l4 with the result that a given portion of the disc takes a relatively long time to pass from one field to the opposite field.

The opposite effect of this principle is utilized when the blocks 84 and ii are close together for it is seen from the full line position of the block in Fig. 4 that it is positioned somewhat to the left of the pole of magnet l3 above it. This tends to concentrate the flux passing through the disc from the pole of magnet l3 to block I5 closer to the opposed field than if the block l5 were directly under the pole of the magnet I3. The present armature accomplishes the concentrating efiect even better than if it extended the full width of the magnet because of the fact that the blocks l4 and IS in their most efiective position are positioned well within the projections of the more remote edges of the pole faces of the magnet l3. The result of this is that the flux emanating from the remote portions of the pole face of magnet l3 instead of tending to pass di rectly downwardly through the disc passes somewhat diagonally and therefore crowds in closer to the center line with the result that the opposed magnetic fields are more concentrated or are concentrated more closely together than with an armature which extends the full width of the magnet.

It will be observed that in the dotted line potil sition of armature ll in Fig. 4 it has passed partially out from under the pole face of the magnet l3. In this position it not only deconcentrates the magnetic fields but also increases the reluctance of the path between the block I! and the magnet l3 by virtue of the fact that less of their adjacent faces are close together. In other words, the block I! in this position acts as sort of a valve to cut off the flow of flux from magnet l3 to the block l5. However, it is apparent that this same cutting off action could occur by moving the block far enough in the opposite direction. The length of the block l5 and the position of the block l4 are preferably such that substantially the maximum available damping torque can be obtained before the block l5 reaches a position where the shut off effect between it and the magnet H! is greater than the effects which increase damping torque such as that resulting from the concentrating of the fields. Unless the absolute maximum torque available from a given magnet is required, it is preferred that the blocks reach their most effective position before coming together as this will give a smooth and uniform adjusting effect.

In view of the gradual effect which the movement of the block I! has it isnecessary for this block to be able to move a considerable distance in order to have the desired wide range of adjustment. In the illustrated embodiment of the invention the block I! can be moved entirely beyond the pole of magnet l3 to provide maximum adjustment. This means that the table l6 must be relatively long with the result that there may be some possibility of a flexing of this table as upon application of a downward force to the screw 3|, for example. To prevent such an oocurrence it is desirable to provide some support for the outer end of table It. According to this invention this support is provided by a bracket arm 4| formed as part of a plate 42 and snugly engaging an enlarged portion 43 of screw head 33. The plate 42 is secured to a pair of laterally spaced posts 44 formed on the frame I9. It may be mentioned that the frame I9 is die cast aluminum so that its proximity to the magnets is not objectionable and so that the various special forms thereof may be provided economically. The plate 42 is secured to the posts 44 by screws 46. However, in order to position the bracket 4| quite accurately the plate 42 is positioned by means of pins 48 formed thereon and fitting snugly into holes drilled in posts 44. The plate 42 is also used for supporting the register 49 and a data plate 5| and therefore the provision of the bracket 4| thereon involves very little expense. This plate is also die cast aluminum. I

The provision of the pins 48 for positioning the plate 42 makes it practical to provide slots instead of snugly fitting holes for engaging the screws 46. This is an advantageous feature of convenience since it permits removal of the plate 42 without completely removing the screws 48 even though great accuracy in positioning the plate 42 is obtained by the pins 48.

From the foregoing it is seen that a damping assembly is provided in which the adjustment is dependably constant, being free from variations due to backlash or due to springing of the armature assembly with respect to the magnet. Extremely delicate adjustments may be made with ease partly because of this same elimination of backlash and partly because the adjusting effect of the movable block of the armature is quite gradual, permitting a relatively great movement of the adjusting screw II for a very minute adjusting effect. Furthermore, there is a relatively high degree of uniformity in adjustment throughout the range of adjustment.

The disclosures of this application are illustrative and the invention is not to be limited by them. In fact, if modifications or improvements are not at once obvious, they may be devised in the course of time to make additional use of the broad ideas taught and covered by this application. The claims are intended to point out novel features and not to limit the invention except as may be required by prior art.

I claim:

1. A damping magnet assembly for a rotating disc, including a generally U-shaped magnet disposed to be positioned with its poles adjacent one face of the disc and an armature disposed to be positioned adjacent the other face of the disc opposite the poles of the magnet, said armature including a magnetic bar relatively remote from the magnet poles and magnetic members substantially in magnetic contact with the bar and positioned relatively close to the magnet poles but relatively movable toward and away from each other for altering the damping torque which would be exerted on the rotating disc by the damping magnet assembly.

.2. A damping magnet assembly for a rotating disc, including a generally U-shaped magnet disposed to be positioned with its poles adjacent one face of the disc and an armature disposed to be positioned adjacent the other face of the disc opposite the poles of the magnet, said armature including a magnetic table relatively remote from the magnet, an extension on said table positioned approximately opposite one pole of the magnet, and a movable extension slidable on the table in a position generally opposite the other pole of the magnet and in a direction toward and away from the first named extension.

3. A damping magnet assembly for a rotating disc, including a generally U-shaped magnet disposed to be positioned with its poles adjacent one face of the disc and an armature disposed to be positioned adjacent the other face of the disc opposite the poles of the magnet, said armature including a magnetic table relatively remote from the magnet, an extension on said table positioned approximately opposite one pole of the magnet, and a movable extension slidable on the table in a position generally opposite the other pole of the magnet and in a direction toward and away from the first named extension, the sizes and proportions of the extensions being such that the damping torque exerted on the rotating disc between the magnet and the extensions is initially reduced to a substantial degree by the deconcentration of the adjacent opposed magnetic fields.

4. A damping magnet assembly for a rotating disc, including a generally U-shaped magnet disposed to be positioned with its poles adjacent one face of the disc and an armature disposed to be positioned adjacent the other face of the disc opposite the poles of the magnet, said armature including a magnetic table relatively remote from the magnet, an extension on said table positioned approximately opposite one pole of the magnet, and a movable extension slidable on the table in a position generally opposite the other pole of the magnet'and in a direction toward and away from the first named extension, the sizes and proportions of the extensions being such that the damping torque exerted on the rotating disc between the magnet and the extensions is initially reduced to a substantial degree by the deconcentration of the adjacent opposed magnetic fields, the extensions in their most eflective damping positions being out of contact with one another.

5. A damping magnet assembly for a rotating disc, including a generally U-shaped magnet disposed to be positioned with its poles adjacent one face of the disc and an armature disposed to be positioned adjacent the other face of the disc opposite the poles of the magnet, said armature including a magnetic table relatively remote from the magnet, an extension on said table positioned approximately opposite one pole of the magnet, a movable extension slid'able on the table in a position generally opposite the other pole of the magnet and in a direction toward and away from the first named extension, and means for moving the sliding extension including a screw journaled in a manner to be free from endwise play and engaging threads in the extension with resilient pressure.

6. A watt-hour meter mechanism of the general type including a driving unit, a frame secured to the driving unit, a disc rotatably carried by the frame, a damping magnet carried by the frame with opposed poles adjacent one face of the disc and an armature carried by the frame adjacent the other face of the disc and opposite to the poles, characterized by the division of the armature into two magnetic portions relatively movable in the direction of the spacing between thepoles and which overlap in the direction of the relative movement.

'7. A watt-hour meter mechanism having a driving unit, a frame secured thereto, spaced bearings carried by the frame, a disc rotatably supported by the bearings, a damping magnet carried by the frame with opposed poles adjacent one face of the disc and an armature carried by the frame being secured thereto at a point at one side of the axis of the disc, and having two relatively movable magnetic portions, and means to brace the armature at a point remote from said point whereby the armature will be rigidly mounted even though it be of a substantial length, said bracing means including extensions on said frame and a removable bracket interlocking with the extensions to insure accurate positioning of the bracket.

8. A watt-hour meter mechanism having a driving unit, a frame secured thereto, spaced bearings carried by the frame, a disc rotatably supported by the bearings, a damping magnet carried by the frame with opposed poles adjacent one face of the disc and an armature carried by the frame STANLEY s. GREEN. 

